How forest height affected 18th-century science

January 13th, 2012 by Michon Scott

The new feature story, Seeing Forests for the Trees and the Carbon, discusses the need to form a three-dimensional picture of the world’s forests. Such a three-dimensional picture includes tree canopy height (below). Although canopy height in the Amazon Rainforest doesn’t match those of the Pacific Northwest or Southeast Asia, it still far exceeds the canopy height of Western Europe.

The height differences call to mind the adventures of a European naturalist who set out from Amsterdam in 1699 and spent two years exploring the jungles of Suriname. Bugs were the main attraction; namely, bugs that transformed from caterpillars into moths and butterflies. The scientist became one of the foremost experts on insect metamorphosis, braving tropical fevers, poisonous flora, slave rebellions, and a near shipwreck. What people found most audacious about the expedition was the age (52) and gender of the person who undertook it.

Maria Sibylla Merian was born in 1647 in Frankfurt, Germany, to a family of printers. Besides helping with the family business, she nurtured her interest in bugs from an early age. By the late 1690s, she was living in the bustling metropolis of Amsterdam. Among her many contacts were missionaries who were converting “heathens” half a world away. Merian was invited to visit, giving her the chance to study insects and plants that few other naturalists had ever seen. Teenage daughter in tow, she crossed the Atlantic.

Once she arrived in Suriname, however, Merian faced a challenge she probably hadn’t anticipated. In Germany and the Netherlands, she collected caterpillars from gardens designed for human enjoyment. That meant that her prized bugs could be found on plants that were waist high at most. The tropical jungle was different—not just different from the well-manicured gardens, but from any forests she might have known.

Long before Merian’s time, Europeans had cleared the land on much of their continent, making way for farming and pasture. Suriname, however, was covered in dense forest, with trees soaring 150 feet skyward. Bugs lived high over Merian’s head, completely out of reach most of the time. And in the vertical yards of tree trunk overhead, different insect communities thrived at different levels: The bugs living 30 feet above ground might be completely different from bugs living 60 feet above ground.

She made the most of the situation, collecting and drawing the insects that were within reach, and studying detritus that fell from the forest canopy. In one instance, she even had a mighty tree chopped down to collect its caterpillars and cocoons. Illness forced Merian to cut short her trip, originally planned for five years. She did, however, return to Europe with enough samples, drawings, and notes to assemble Metamorphosis Insectorum Surinamensium (Insects of Surinam), published in 1705.

The same tall tropical trees that occasionally hampered Merian’s research continue to provide homes and food for insects, birds, and mammals today. While Merian could only gaze at the trees from the ground, modern satellite sensors can monitor the trees from above, gauging their height, and helping scientists understand how much carbon they hold.

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